This application claims priority to German patent application number 19935251.8 entitled xe2x80x9cAnwendung TiO2-haltiger partikulxc3xa4rer Materialien fxc3xcr feuerfeste Enzeugrissexe2x80x9d, filed Jul. 27, 1999.
The invention relates to the use of particulate materials containing TiO2 as an additive in refractory products consisting of a mixture of aggregate substances and at least one binding agent.
Refractory products are based substantially on the six base oxides, SiO2, Al2O3, MgO, CaO, Cr2O3 and ZrO2 and on compounds thereof, occasionally in combination with carbon or graphite. As for the carbon, silicon carbide is used and, in small amounts for special applications, boron carbide and nitrides. Refractory products are used for lining large areas of apparatus for thermal processes, such as melting, burning and heating apparatus, as well as transporting vessels, especially in the iron and steel industry, among other things; they are usually installed behind a casing, either as they are or after the addition of liquid, and after they become hard they are used for the seamless casing of apparatus. These unshaped refractory products are divided into refractory concretes, plastic compositions, ramming masses, taphole plugging material, compositions for spray application, mortar, dry compounds, forcing masses and plasters for surface protection. The binding agents are hydraulic curing substances, such as cement, alumina refractory cement and electrofilter ash, as well as inorganic substances curing by chemical reaction.
Refractory linings are subjected to considerable wear and tear by corrosion and infiltration by metallurgical slags and molten metal. Corrosion is caused by chemical attack by the furnace charge, the molten metal, the molten slags and/or the furnace dust. Reaction products form, including eutectic melts, which run down or drip. In the case of infiltration, slags or reaction melts penetrate by capillary forces into the pores of the refractory lining. Due to the temperature gradient present in a refractory lining the melt penetrates into it deeply until it hardens. During solidification, molten substances of a low solidification temperature form which migrate further toward the cold side of the refractory lining. Thus a division occurs into zones of varying chemical and mineralogical composition. A similar zoning develops when components of the melt form mixed crystals with components of the refractory lining and are thereby withdrawn from the melt. As a consequence, cracking and spalling occur when temperature changes occur.
The present invention is addressed to the problem of improving refractory products, especially unshaped products, especially with regard to consistent material quality and unvarying chemical composition by new combinations of materials, in order thereby to reduce wear due to corrosion and infiltration, and being able to offer tailored solutions of problems.
The solution of this problem is accomplished by the use of particulate materials containing TiO2, as an additive for refractory products consisting of a mixture of aggregate materials and at least one binding agent.